# GPT-6 Luna

> GPT-6 Luna is the volume tier of OpenAI's GPT-6 family, released in September 2026 alongside GPT-6 Sol. It carries improvements from GPT-6 Astra into a model built for speed and throughput, and is meant for work that runs constantly: extraction, classification, routing, first-pass summarization, and the cheap legs of an agent loop.

Canonical: https://routemux.com/openai/gpt-6-luna
Provider: OpenAI

## Key facts

| Field | Value |
| --- | --- |
| Model ID | openai/gpt-6-luna |
| Official model ID | gpt-6-luna |
| Context window | 1.1M |
| Max output | 128K |
| Input modalities | text, image |
| Output modalities | text |
| Capabilities | Vision, Reasoning, Tool Calling, Coding, Cache, Paid Cache Write, Normalize Openai Envelope, Strip Responses Summary Input |
| Upstream release | 2026-09-22 |
| Availability | available |

## Pricing

- RouteMux input: $0.03 per 1M tokens
- RouteMux output: $0.15 per 1M tokens
- Official input: $0.1 per 1M tokens
- Official output: $0.5 per 1M tokens
- Cache read: $0.003 per 1M tokens
- Cache write: $0.0375 per 1M tokens
- Saving vs official: 70%
- Official price source: openai_x0.30, verified 2026-09-23

Billing is prepaid wallet, charged per successful request only.

## API access

Base URL: https://api.routemux.com

Supported protocols:

- openai_chat
- openai_responses
- anthropic_messages

## What is GPT-6 Luna

GPT-6 Luna is the volume tier of OpenAI's GPT-6 family, released in September 2026 alongside GPT-6 Sol. It carries improvements from GPT-6 Astra into a model built for speed and throughput, and is meant for work that runs constantly: extraction, classification, routing, first-pass summarization, and the cheap legs of an agent loop.

It is not a stripped-down model. It accepts text and image input, supports tool calling and explicit prompt caching, and exposes reasoning effort as a request parameter from none all the way to max, so the same deployment can answer trivial turns with no reasoning and still think hard when a step needs it.

Through RouteMux it is $0.03 per 1M input tokens against OpenAI's $0.10, and $0.15 against $0.50 on output. It is reachable over OpenAI Chat Completions, OpenAI Responses, and Anthropic Messages, so switching an existing client to Luna is a model-string change.

## Key capabilities

- **Built for volume** — Priced and tuned for high-throughput work where per-million cost matters more than peak capability.
- **Reasoning from none to max** — Effort is a request parameter; set none for plain completions or raise it for the occasional hard step.
- **Vision and tools included** — Image input, tool calling and explicit prompt caching are all supported.
- **Three protocols** — OpenAI Chat, OpenAI Responses, and Anthropic Messages all route to this model.

## Other variants in this family

- GPT-6 Astra (`openai/gpt-6-astra`)
- GPT-6 Sol (`openai/gpt-6-sol`)

## Sources

- [OpenAI — Models](https://platform.openai.com/docs/models)
- [OpenAI — API pricing](https://developers.openai.com/api/docs/pricing)

_Content reviewed by Jerry Fan on 2026-09-23._